[10p-N403-1~17] 9.2 Nanoparticles, Nanowires and Nanosheets

▲ [10p-N403-12] Highly pure monoclinic beta molybdenum trioxide synthesized by a mini
furnace device utilizing a vapor rapid cooling mechanism

〇(D)Ngo Minh Chu¹, Nguyen Duy Hieu¹, Thi Mai Dung Do¹, Tadachika Nakayama¹, Koichi Niihara¹, Hisayuki Suematsu¹ (1.Extreme Energy-Density Research Institute, Nagaoka University of Technology)

Keywords:monoclinic beta molybdenum trioxide, thermal vaporation method

β-MoO₃ is a low-temperature phase of MoO₃, which has many applications in electronics, optical devices, gas sensors, semiconductors, and nuclear medicine. From our previous research, β-MoO₃ was synthesized by pulsed wire discharge (PWD). However, β-MoO₃ synthesized from the PWD method still had some impurity of Mo and α-MoO₃. Therefore, in this report, by utilizing the β-MoO₃ formation mechanism of rapid cooling vapor in PWD, we have made a mini furnace, much smaller than a regular tube furnace, with a higher temperature gradient than that of conventional furnaces. α-MoO₃ powder (99.9% purity) from Nilaco Co., Ltd was evaporated in the mini furnace at different temperatures (T_f) from 750 to 1000 °C under the oxygen gas flow. Samples were collected by micro membrane filters at a position with a temperature of about 60 ºC and were characterized by X-ray diffraction. From these results, high purity β-MoO₃ powder was obtained at temperatures above 800 °C. Comparing with β-MoO₃ made by PWD, peaks of α-MoO₃ at 27.3º was disappeared. At 750 °C, which is the temperature where MoO₃ starts to evaporate. From temperature distribution results inside the tube, the temperature gradually decreased from inner to outer in the tube. The temperature gradient increased with the increase in T_f, which might make the purity of β-MoO₃ high at higher T_f. From these results, the mass production of β-MoO₃ powders for promising applications can be obtained by utilizing the mini furnace system.